All cheats enabled
Enter "BOBBYBIRD" as a code. Note: Enter "ZBOBBYBIRD" in the EU/PAL version of the game.

Level select
Enter "THEEARTHMOVED" as a code.

Invincibility
Enter "ASSMAN" as a code.

All weapons
Enter "FATKNACKER" as a code.

Unlimited ammunition
Enter "FATTERKNACKER" as a code.

All characters in multi-player mode
Enter "OMGTKKYB" as a code.

Officer Barbrady
Enter "ELVISLIVES" as a code.

Mr. Mackey
Enter "CHEATINGISBAD" as a code.

Phillip
Enter "PHAERT" as a code.

Terrance
Enter "RAFT" as a code.

Mr. Garrison
Enter "DOROTHYSFRIEND" as a code.

Chef
Enter "LOVEMACHINE" as a code.

Wendy
Enter "CHECKATACO" as a code.

Pip
Enter "FISHNCHIPS" as a code.

Ike
Enter "KICKME" as a code.

Mrs. Cartman
Enter "ALLWOMAN" as a code.

Mephisto
Enter "GOODSCIENCE" as a code.

Jimbo
Enter "STARINGFROG" as a code.

Ned
Enter "HAWKING" as a code.

Big Gay Al
Enter "OUTRAGE" as a code.

Alien
Enter "MAJESTIC" as a code.

Starvin Marvin unlocked
Enter "SLAPUPMEAL" as a code.

Skinny mode
Enter "VEGGIEHEAVEN" as a code.

Big head mode
Enter "MEGANOGGIN" as a code.

Pen and ink mode
Enter "PLANEARIUM" as a code.

View credits
Enter "SCREWYOUGUYS" as a code.

Extra Speed
By holding C-up and either C-left or C-right, and running at an angle you can move at an increased speed.

Load Your Earned Characters
This allows you to load all of the characters you earned without entering all of the passwords. First, go to Story Mode, and choose load a game. Load the game, then once it starts quit it. Now all of your characters are available in multiplayer.